1. Field of the Invention
This invention relates to a video signal recording method wherein a screen to be displayed in accordance with a high definition television system is divided into a plurality of screens and video signals of such divisional screens are individually converted into video signals according to a current television system and recorded on a plurality of record media.
2. Description of the Prior Art
As a novel television system which may replace a current television system, high definition television systems such as for example, a high vision system, have been proposed which can achieve not only improvement in quality of a screen and quality of sound but also high visual psychological effects such as an ambience feeling or an impressive feeling which are far above those of a current television system.
Since the high vision system is very different in screen system, scanning system and voice system from those of a current television system, for example, the NTSC system, it is impossible to reproduce a high vision signal as it is using an image receiving apparatus or television set of the NTSC system. Thus, a high vision to NTSC converter (down converter) has been proposed wherein a high vision signal is converted into an NTSC signal absorbing differences in effective scanning line number, aspect ratio, horizontal scanning frequency and so forth between the two systems.
FIGS. 8a and 8b illustrate examples of an output image of a down converter. In particular, referring first to FIG. 8a, there is shown a mode wherein 1,035 effective scanning lines of the high vision are reduced to about one half and allotted to 483 effective scanning lines of the NTSC system and picture elements of 10% on each of left and right sides of an image are deleted to obtain an NTSC image without changing the aspect ratio of 4:3 of the NTSC system. Such left and right portions to be deleted, however, can be selected arbitrarily. On the other hand, FIG. 8b shows another mode wherein 1,035 effective scanning lines of the high vision are reduced to about one third and allotted to 362 effective scanning lines of the NTSC system to obtain an image of the NTSC system without changing the aspect ratio of 16:9 of the high vision, and while 10% of a screen at each of upper and lower portions makes a marginal area, the composition of a screen coincides with that of a screen of the high vision.
In a system which employs such a down converter as described above, however, since the number of scanning lines of the high vision is reduced to convert a high vision signal into an NTSC signal, reproduction of an image of a high picture image quality cannot be anticipated, and particularly in a mode wherein left and right portions of an image are deleted, an image of a composition intended with the high vision cannot be obtained.
Therefore, the present applicant has proposed a video signal recording method (Japanese Patent Application No. 1-43171) as a method by means of which an image of a high picture image quality based on the high vision can be displayed on an NTSC image receiving apparatus while maintaining such high quality.
According to the method, a screen of the high vision is divided into a plurality of screens, and high vision signals of the thus divided screens are individually converted into NTSC signals and recorded on record media. Next, the recorded record media are reproduced simultaneously to reproduce the image of a high picture image quality on an NTSC image receiving apparatus. With this method, a high definition image can be displayed on a large screen in sufficient luminance.
Referring now to FIGS. 9a, 9b and 9c, there is shown construction of a screen illustrating a principle of the method. A screen of the high vision is specified such that the aspect ratio is 16:9 and the number of scanning lines in one frame is 1,125 among which the number of scanning lines of an effective screen is 1,035 (FIG. 9a). On the other hand, a screen of the NTSC system is specified such that the aspect ratio is 4:3 and the number of scanning lines in one frame is 525 among which the number of scanning lines of an effective screen is 483 (FIG. 9b).
A screen of the high vision is thus divided into three sections in a vertical direction and divided into four sections in a horizontal direction so that it is divided totally into 12 screens. High vision signals of the screens #1 to #12 obtained by such division are individually converted into NTSC signals and recorded on 12 video disks. Then, if the 12 video disks are reproduced simultaneously with 12 NTSC image receiving apparatus, and the aspect ratio of each of the divisional screens is 4:3, the aspect ratio of the entire screen is 16:9 which coincides with the aspect ratio of the high vision (FIG. 9c). In this instance, if a projection unit for the multi-display is used as an NTSC image receiving apparatus, a high vision display having a sufficiently high brightness for the practical use can be obtained on the NTSC image receiving apparatus while maintaining the high definition on a large screen.
With this method, however, since a video signal is recorded in the form of a composite signal, color phase irregularity appears in a reproduced image due to time base fluctuations of video disks, which deteriorates the quality of a picture image and is not preferable.